Uniformly illuminated meter indicator

ABSTRACT

A cup-shaped meter case made of a light conductive material has a light source mounted interior of the bottom surface thereof. The edge of the case is terminated in an inwardly directed, in cross-section generally triangular, rim. The edge of the case is additionally beveled on both the inner and outer surfaces to direct light conducted from the light source through the case side into the triangular rim from where it is dispersed both inwardly and outwardly of the case to illuminate a dial suitably located outwardly of the rim and to illuminate a meter plate and needle located inwardly of the rim. In one alternate embodiment the case side is shown separated from the case bottom so that the rim may be rotated with respect to the light source. In a further embodiment a separate dial plate is shown fitted over the rim and rotatable thereon.

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SEARCH ROOM 1 Unlted Stat 1 1151 3,699,915

Greene SUBSTITUTF Fitment/ 1r 4 [45] 1972 [54] UNIFORMLY ILLUMINATEDMETER 2,837,053 6/1958 Viret ..1 16/129 INDICATOR 2,953,668 9/1960Bassett, Jr ..240/1 BL X [72] Inventor: William H. Greene, Pompano3,257,748 6/ 1966 Hardesty ..40/130 Beach Primary Examiner-Louis J.Capozi [73] Assignee: The Bendix Corporation, Ft. Lau- AttorneyBruce L.Lamb et al.

- derdale, Fla. 1

5 [22] Filed: May 19, 1971 7] ABSTRACT A cup-shaped meter case made of alight conductive [21] -N" 144946 material has a light source mountedinterior of the v .bottom surface thereof. The edge of the case is ter-52] us. c1. ..116/129 L, 73/431, 240/1 EL, 4 minated in an inwardlydirected, in cross-section v 240/21 generally triangular, rim. The edgeof the case is addi- [51 1m. 01. ..G01d 11/28 fionally beveled on boththe inner and Outer Surfaces [58] Field of Search ..1 16/129, 129 L,124.4; to direct light conducted from the light Source through 240/1 EL,2 B, 2 M, 2.1; 73/431; 324/115, the case side into the triangular rimfrom where it is 156. 40/130 dispersed both inwardly and outwardly ofthe case to v illuminate a dial suitably located outwardly of the rimand to illuminate a meter plate and needle located in- [5614 ReferencesCited wardly of the rim. In one alternate embodiment the UNITED STATESPATENTS case side is shown separated from the case bottom so v that therim may be rotated with respect to the light ..l L Source. In a furtheremb i a Separate p e Smpson is-shown fitted over the rim and rotatablethereon.

2,837,052 6/1958 Viret ..1 16/129 4 Claims, 5 Drawing Figures BACKGROUNDOF THE INVENTION This invention relates to illuminated meters and moreparticularly to those meters whose faces including needles, meter platesand dials are required to be uniformly illuminated.

There has been a requirement that certain meters, particularly aircraftinstrument meters, be uniformly illuminated over their entire face. Thishas been accomplished by specially formed, wedge-shaped meterwincentrally located, as shown, or offset. The case side 16 is suitablyof a thinner material than the case bottom and terminates in an edge 18.The edge is finished in a beveled surface 20 at its outer end.Projecting inwardly from the edge is a rim 22 which is seen to begenerally triangular in its cross-section. The outside surface22a I ofthe rim is generally perpendicular to the longitudinal dows which areedge-illuminated. This particular shape allows the light conductivethrough the window to be evenly dispersed upon the meter face. Thespecial difficult and expensive to manufacture. Additionally, the lightsources for edge illuminating the windows are normally located at thefront panel in which the meter is mounted thus tending to contribute toa general cluttered appearance of the aircraft instrument panel.

SUMMARY OF THE INVENTION The present invention provides a uniformlyilluminated meter through the use of a cup-shaped meter case made of alight conductive material and which has a generally thickened bottomsection in which a light source is mounted. Light is uniformly conductedthroughout theinterior of the meter case material. A specially shapedrim at the edge of the case intercepts the conducted light and dispersesit outwardly of the rim to illuminate a dial situated in that vicinityand also inwardly into the bowl of the case to illuminate a suitablypositioned meter plate and needle. A plain, transparent cover plate maynow be used to cover and protect the meter face.

' Other embodiments of the invention are shown which permit the case rimto be rotated with respect to the light source while preserving theuniform illumination of the meter face.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partly sectional side viewof a meter case illustrating the principles of the invention.

FIG. 2 is a front view of the meter case of FIG. I but with the metermovement removed.

FIG. 3 is a partial view illustrating an alternate embodiment of theinvention wherein the case side is split' transversely from the cupbottom.

FIG. 4 shows another embodiment of the invention, in partial section,wherein a separate rim is provided over the case rim, rotatable thereonand illuminated thereby.

FIG. 5 shows in greater detail the shape of the meter case rim and itseffect upon the light path.

DESCRIPTION OF THE PREFERRED EMBODIMENT I Referring to the figureswherein like reference numerals refer to like elements and referringparticularly to FIG. 1 there is seen a meter case made of a lightconductive material, suitably plexiglas, in the form of a cup that isgenerally a volume of revolution. The meter case 10 includes a thickenedbottom section 12 having an aperture 14 in which is inserted a lightsource, suitably a light bulb 15. Aperture 14 may optionally be r shapeof the meter windows makes them particularly axis 11 of the meter case.The inner surface 22b of the rim is inclined at a shallow angle fromsurface 22a. The surfaces 16a and 16b of side 16 are generally parallelto the longitudinal axis of the case. However, the inner surface of caseside 16 in the vicinity of rim 22, that is at the surface designated25a, is directed inwardly so that perpendiculars taken from the surface,for example, perpendicular arrows 30 and 31 are directed at meter card33 and needle 34 of meter mechanism 35 which is mounted on a boss 18inside the case. Thus, light moving through side 16 is reflected againstbeveled surface 20 into the triangular shaped rim 22 and onto surface25a from whence it is dispersed through that surface onto the meter facecomprised of meter card 33 and needle 34. Additionally, a portion of thelight is reflected at inner surface 22b and dispersed through outsidesurface 22a.

Reference should now be made to FIG. 5 which shows the meter case edgein greater detail and its effect upon the light path. As shown, beveledsurface 20 is at an angle A with respect to side 16 while inner surface22b is inclined at an-angle of A to side 16. Light is conducted throughthe meter case material generally along paths parallel to arrow. 17 toreflect against beveled surface 20 to be transmitted through innersurface 221). Knowing the refracture index of the meter case material,A, and A can be chosen such that the light transmitted through innersurface 22b is directed at or near the center needle 34 and meter card33.

Referring now to FIG. 2 which is a front view of the meter case of FIG.1 with meter mechanism 35 removed, there is seen indicia on rim surface22a..This indicia might be dark to show against the lighted rimbackground or even more suitably might be frosted so as to show lightedon a dark background. Boss 18 is seen to have two suitable holes 18a and18b for mounting meter mechanism 35.

Refer now to FIG. 3 where the invention is embodied in a form' whichpermits the rotation of rim 22 about the longitudinal axis of the meterwithout rotating the light source. It can be seen that side 16 has beencut along a plane perpendicular to the longitudinal axis of the meter toform a discontinuity 40 in the side. It can be seen that the sides ofthe discontinuity are parallel to one another and are suitably polishedfor maximum light transference thereacross. Light will now be conductedfrom bottom section 12 across discontinuity 40 and into side 16. Themeans by which the meter face is illuminated are identical to thosedescribed earlier.

Referring now to FIG. 4 where meter case 10 is essentially identical tothe meter case 10 of FIG: 1 and where additionally a ring dial 45 havinga dial face 45b generally parallel to rim surface 22a and a turned-downsection 45a generally perpendicular to surface 45b, and whichturned-down section encircles the meter case 10 so as to be rotatableabout the meter case longitudinal axis. In this embodiment theillumination of the meter plate and needle as shown in FIG. I isidenticalto that an inwardly directed annular rim section having an Icute" face generally co-extensive with said end surface and an innerfaceforming a shallow angle with said outer face and forming an intersectionwith said side portion interior surface, said side portion in thevicinity of said intersection being inwardly directed at a shallow anglewith respect to the interior surface of said side portion generally.

2. The cup-shaped case of claim 1 with additionally indicia placed onsaid end surface.

3. The cup-shaped case of claim 1 with additionally an annulardiscontinuity in said case generally perpendicular o the lightconductive paths in said material.

4. The cup-shaped case of claim 3 with additionally indicia placed onsaid end surface.

1. A cup-shaped case made of a light conductive material comprising: afirst section having light receiving means located therein; a sideportion having exterior and interior surfaces and terminating in an endsurface, the intersection of said end surface with said exterior surfacebeing beveled; and, an inwardly directed annular rim section having anouter face generally co-extensive with said end surface and an innerfaceforming a shallow angle with said outer face and forming an intersectionwith said side portion interior surface, said side portion in thevicinity of said intersection being inwardly directed at a shallow anglewith respect to the interior surface of said side portion generally. 2.The cup-shaped case of claim 1 with additionally indicia placed on saidend surface.
 3. The cup-shaped case of claim 1 with additionally anannular discontinuity in said case generally perpendicular o the lightconductive paths in said material.
 4. The cup-shaped case of claim 3with additionally indicia placed on said end surface.